1. Field of the Invention
The present invention relates to a power supply having a standby mode, during which the electric power consumption is reduced.
2. Description of Related Art
Electronic appliances such as a television and a video cassette recorder (VCR) employ a switched-mode power supply (SMPS) as a power supply and include an operating mode and a standby mode in order to implement a high function, for example, a remote control function and a timer function. The operating mode is a mode in which the appliance being on, the power supply delivers the average power which is needed for the appliance to work properly. In the standby mode, the appliance is off, but only minimum function circuits such as a timer and a microprocessor are still powered. For example, a television goes to a standby mode when a main power is turned off, so that minimum function circuits such as a microprocessor are still powered. Then, when a main power is supplied to the television by a remote controller or a timer, an electrical power is supplied to a tuner, a voice and image processing portion, a CRT (cathode-ray tube) driving portion, etc., to output a television broadcasting. Therefore, in the standby mode, power consumption occurs continually unless a plug is completely separated from a plug-socket.
For example, if it is assumed that an electric power is 50 W (watts) in the operating mode and 2 W in the standby mode, an electric power of 4% is consumed in the standby mode. If it is assumed that a television set is operated for three hours, it is in standby mode for twenty one hours. Power consumption in the operating mode is 3 hoursxc3x9750 Watts=150 Watt-hours, power consumption in the standby mode is 21 hoursxc3x972 Watts=42 Watt-hours. Power consumption is 192 Watt-hours a day. Therefore, power consumption in the standby mode is 22% of 192 Watt-hours, about a quarter (xc2xc). An annual power consumption of one television set in the standby mode is as much as 15,330 Watt-hours.
In recent years, power saving electronic appliances have been strongly required for the purposes of saving resources. Therefore, manufacturers of electronic appliances such as TV (television) and VCR (video cassette recorder) undergo much research to reduce power consumption in the standby mode. There are various kinds of conventional techniques to reduce power consumption in the standby mode. The conventional technique includes a method in which an auxiliary low power terminal is added for a power saving in the standby mode, an output voltage drop method, an output terminal current open method, a switching frequency decreasing method (burst mode operation), etc. The conventional techniques have the following problems.
In the case of a method having an auxiliary low power terminal added, since the auxiliary power terminal should be added separately from the main power terminal, there is a problem that a production cost increases. Also, in case of the output voltage drop method, power saving efficiency and reliability are low. In the case of the output terminal current open method, since parts are added, the production cost increases and power saving efficiency is low. Lastly, in the case of the switching frequency decreasing method (burst mode operation), a turn-on loss decreases and an audible noise occurs.
In a power supply using the voltage drop method according to earlier art, since the power supply is designed centering on the operating mode having a high load capacity, power conversion efficiency in the standby mode is significantly lowered. Also, the switching control circuit has a function to lower an output voltage, but this merely reduces an output voltage at a second output of the transformer in order to reduce a load power. Therefore, the power supply according to the earlier art is low in power conversion efficiency and power saving efficiency.
Exemplars of the background art are U.S. Pat. No. 6,151,224 issued to Lim et al. for Power Supply with Reduced Power Comsumption in Standby Mode, U.S. Pat. No. 6,043,994 issued to Keller for Power Supply Having a Transformer for Standby Mode Operation, U.S. Pat. No. 5,126,930 issued to Ahn for Switched Mode Power Supply Controller Having a Stand-by State Using a Frequency Divided Burst Mode, U.S. Pat. No. 6,157,549 issued to Nath for Power Supply with Multiple Mode Operation, U.S. Pat. No. 5,351,177 issued to Megeid for Switch Mode Power Supply with Standby Mode Operation, U.S. Pat. No. 5,920,466 issued to Hirahara for Switching Power Supply Unit, U.S. Pat. No. 5,812,383 issued to Majid et al. for Low Power Stand-by for Switched-mode Power Supply Circuit with Burst Mode Operation, U.S. Pat. No. 5,041,964 issued to Cole et al. for Low-Power, Standby Mode Computer, U.S. Pat. No. 5,278,654 issued to Yang for TV Power Supply Control Method and Circuit with Automatic Standby Mode, and U.S. Pat. No. 5,375,247 issued to Hueser for Apparatus for Controlled Switching of a Microcomputer to Standby Mode.
It is therefore an object of the present invention to provide a power supply having a low power consumption and a high power saving efficiency.
It is another object to provide a power supply having production cost minimized while having power savings efficiency maximized.
It is still another object to power supply that is easy to manufacture and yet be highly efficient.
In order to achieve the above and other objects, the preferred embodiments of the present invention provide a power supply, including an operating power circuit outputting an operating voltage, a standby power circuit outputting a standby voltage, a starting switching circuit having a first remote control receiver for receiving a first remote control signal and supplying a starting power to the standby power circuit in response to the first remote control signal, a controller having a second remote control receiver for receiving a second remote control signal and performing a function corresponding to the second remote control signal, and a feedback circuit processing a control signal to switch the starting switching circuit to either of a standby mode and a power saving mode in response to a power offsignal from either of the second remote control receiver and a power switch.
The preferred embodiment of the present invention further provides a power supply, including an operating power circuit outputting an operating voltage, a standby power circuit outputting a standby voltage, a starting switching circuit having a remote control receiver for receiving first and second remote control signal and supplying a starting power to the standby power circuit in response to the first remote control signal, a controller performing a function corresponding to the second remote control signal, and a feedback circuit processing a control signal to switch the starting switching circuit to either of a standby mode and a power saving mode in response to a power off signal from either of the second remote control receiver and a power switch.
The power supply further includes a power input circuit supplying a first direct current voltage; a power transformer having a first winding, a second winding, a third winding and a fourth winding, the third winding connected to the operating power circuit, the fourth winding circuit connected to the standby power circuit; an auxiliary power circuit connected to the second winding of the power transformer and rectifying a voltage induced from the first winding to the second winding to a second direct current voltage; and a switching control circuit receiving the second direct current voltage of the auxiliary power circuit and switching a current flowing through the first winding of the power transformer into a high frequency current, where the high frequency current generate on the first winding of the power transformer is induced to both the third winding and the fourth winding of the power transformer.
The starting switching circuit further includes a switching unit having a starting resistor, a first resistor serially connected to the starting resistor, a first capacitor serially connected to the first resistor, a diode having one end serially connected to the first capacitor and the other end connected to one end of the first remote control receiver, and a zener diode having one end connected to the other end of the diode and one end of the first remote control receiver and the other end earthed (grounded); a starting power unit having a first transistor including an emitter electrode connected to the starting resistor, a collector electrode connected to the switching control circuit and a base electrode, a second transistor including an emitter electrode earthed, a collector electrode connected to the base electrode of the first transistor and a base electrode, a third resistor having one end connected to the other end of the first remote control receiver and the other end connected to the base electrode of the second transistor, a fourth resistor having one end earthed and the other end connected between the second transistor and the third resistor, and a second capacitor one end earthed and the other end connected between the second transistor and the third resistor.
The feedback circuit excessively increases a feedback current in response to the power off signal to reduce a switching on time of the switching control circuit, so that a voltage of the auxiliary power circuit falls down sufficiently to turn off the switching control circuit.
The preferred embodiment of the present invention further provides a method of reducing power consumption in a power supply having a standby mode, an operating mode and a power saving mode. The method includes receiving a power on signal from either of a first remote control receiver and a power switch in the standby mode; starting by supplying an initial starting voltage to switching control circuit when the power on signal is received; generating either of a standby voltage and an operating voltage by a switching operation of the switching control circuit; receiving a power off signal from either of a second remote control receiver and the power switch in the operating mode; and turning off the switching control circuit in response to the power off signal.
The method further includes checking whether the standby voltage is needed in response to the power off signal; and performing the power saving mode by turning off the switching control circuit when the standby voltage is not needed.
Using the power supply according to the preferred embodiments of the present invention, since only the start switching circuit having power consumption of several mWh (milliwatt-hours) is operated in the standby mode and other circuit portions is not powered, power consumption can be minimized in the power on remote control signal receiving standby state. Further, since the preferred embodiments of the present invention can constitute the power saving mode by adding several parts and the remote control receiver, the production cost can be minimized and the power saving efficiency can be maximized.